Validate date with Datejs

Datejs is an open source JavaScript Date library for parsing, formatting and processing.
Website: http://www.datejs.com

 
function isValid(date, pattern){
    if(pattern == null){
      return false;
    }
    var parseExact = Date.pareExact(date, pattern);
    if(parseExact !== null){
      return true;
    }
    return false;
}

Another popular date library is Moment.js